Electroplating sequence



Patented Feb. 1935 ELECTROPLATING SEQUENCE George B. Hogaboom, NewBritain, 001111., assignor to Hanson-Van Winkle-Munning Com- P ly,Jersey Matawan, N. J.

, a corporation oi New No Drawing. Application December 30, 1933, SerialNo. 764,788

8 Claims. (Cl. 204-43) a This invention relates in general to theplating of articles or surfaces of base metals such as, for example,iron, copperand its alloys, zinc and the like. More particularly, theinvention resides in a new and improved electroplating se-- quence inwhich nickel deposits are employed as finishing or preparatory layers,as for example where the finished surface is to be a nickel surface, orwhere the finished surface is to be a chromium surface on nick Twogeneral classes of nickel plating are well recognized in the art,namely, the ordinary white nickel and the so-called bright nickel. Ingeneral, the white nickel deposit requires buifing to bring up a highlustre, whereas thebright nickel does not There is a well recognizeddifficulty in securing firmly adherent deposits of bright nickel on basemetals, under ordinary conditions, due to the fact that such brightnickel deposits are always under a considerable stress or tension whichreduces their power to permanently adhere to the base metal, andespecially so when a bright nickel is used as a preparatory coatingfollowed by a finishing electrodeposit ofchromium, which introducesstill furtherstress or stresses tending to cause the bright nickeldeposit to crack and peel from the under surface to which it isattached. This dificulty in the field of chromium plating, for example,is in-= deed so great that it is substantially correct to state thatbright nickel deposits have not been successfully employed aspreparatory deposits on which to apply chromium plating.

I have discovered that the difiiculty of obtaining satisfactoryadherence and permanence in bright nickel deposits, whether as finishingor preparatory layers, is satisfactorily overcome by interposing a layerof white nickel between the base metal and the bright nickel, so thatthe bright nickel lies adjacent to the white nickel, which latter may bedirectly on the base metal of which the article is composed, 'or uponany approved preparatory coating as used, for example, in standardplating cycles or sequences. Thus, in chromium plating, where it hasbecome more or less standard practice to deposit nickel on the basemetal of the article, then copper and then nickel, as a preparatorysequence for receiving chromium, I may for example deposit on the basemetal of the article a preliminary deposit of white nickel, then copper,then a second layer of white nickel, followed by a layer of brightnickel and finally chromium. These preliminary deposits before thechromium may all 5 be applied without subsequent bufllng, where thearticle itself has been properly buffed initially. By reason of the highlustre of the bright nickel surface, the deposited chromium will beobtained in a satisfactory lustrous state. The white nickel next to thebright nickel deposit, appears to act 5 somewhat as a primer coat, whichwithstands the tension of the bright nickel coat, so that even under thestress or tension of the subsequently deposited chromium layer thecomposite layers-adhere firmly.

In practicing the invention, any of the standard white nickel and brightnickel solutions may be employed, either of the single salt type or ofthe double salt type, as given for example in Principles ofElectroplating and Electroiorming, by Blum and Hogaboom, the brightnickel solution containing a suitable addition agent or brightener, suchas for example gum arable, gum tragacanth, or any of the other materialswell-known for this purpose. The work to be plated is first polished andbuffed, then thoroughly cleaned and rinsed, in accordance with wellunderstood practice, and thereafter passed through the plating sequence.This plating sequence, white nickel, bright nickel, chromium,characteristic of my present invention, may be preceded by one or moreother deposits, which need not be here specifically described. Withrespect to the white nickel, bright nickel, chromium sequence, it willbe understood thatsthe plating operations will be conducted under propercurrent density, temperature and other conditions known to those skilledin this art, for the avoidance of coarsely granular or cloudy deposits,so that the resultant finish of the chromium plated article will havethe desired bright lustre. Any of the standard chromium platingsolutions may be used, for example, the well-known chromic acidsolutions. I

The invention comprises in its broader aspect the sequence of brightnickel on white nickel deposits, whether the white nickel is applieddirectly on the base metal object or on an intervening preparatoryelectrodeposit, and whether the bright nickel is to serve as a finishingsurface or as a preparatory surface for some other deposit, such as forexample chromium. The invention also includes, as a particularlyimportant specific embodiment, the sequence of white nickel, brightnickel and chromium. In this latter specific embodiment, the whitenickel may likewise be directly on the basev metal of the article, or onan intervening preparatory electrodeposit such as, for example, cyanidecopper on iron, or white nickel, then acid copper, on iron, 55

or any of the other standard preparatory de- .posits on iron, copper andits alloys, zinc. and

the like.

I claim:---

l. The method of electroplating, which comprises depositing a layer ofwhite nickel; followed by a layer of bright nickel. I

2. The method of electroplating, which comprises depositing a layer ofwhite nickel, followed by a layer of bright nickel, and then a layer of?chromium.

3. The method of electroplating, which comprises depositing a layer ofcopper, then a layer of white nickel, and next a layer of bright nickel.4. The method of electroplating, which com-

